1. Field of the invention
This invention relates to the field of the cold rolling of strip, and particularly to the field of the cold rolling of steel strip by temper mills.
2. Description of the prior art
When metal strips are rolled by temper mills, the cleaning of the surface of the rolls is required to maintain the surface quality of the strip products and to avoid defects associated with the rolling. One of the cleaning methods is the constant removal of the foreign objects on the surface of the rolls by various means of brushing.
Japanese Patent Publication laid open No. 57-75212 discloses a method wherein brushing rolls are used for loosening particles from the surface of the work rolls, and exhausting means are used to remove the objects from the rolling system. However, in this disclosed invention, the removal is limited to the foreign objects on the surface of the work rolls. Accordingly, the complete removal of the objects is not attained because foreign objects on the surface of the back up rolls may contaminate the surface of the strip. To produce a strip with a matte surface, the surface of the work rolls has comparatively large roughness of surface, and the hardness of the surface of the back up rolls is lower than that of the work roll, which causes the generation of abrasive powders from the contact of the work roll with the back up roll. The contact pressure between the work roll and back up roll is higher than that between the work roll and the strip, which causes the generation of the abrasive powders. Moreover, when the mill is driven by work roll, or top or bottom back up roll, the contact surface between the rolls slips, which causes the generation of the abrasive powders. This necessitates the constant removal of the foreign objects on the surface of the work roll and the back up roll to prevent contamination and resultant surface defects of the strip.
This prior art method has the problem that the brushing ability or the suction of the exhausting means can deteriorate; also exhausting ducts may contact the brushing rolls when the diameter of the brushed roll or the diameter of the brushing roll are changed. Another problem in the prior art method is that of scratch marks on the surface of the rolls, caused by the bristles of the brushing rolls. When the rolls of the mill are stopped one roll may continue to rotate while another roll has stopped. Another problem is the positioning of the brushing rolls when the rolls of the mill are changed and the brushing device includes exhaust duct which move forward or backward. In this situation the positioning of the new brushing rolls must be adjusted to work with the brushing rolls and the exhaust system.
Japanese Utility Model Publication laid open No. 54-101074 discloses a method wherein air blowing holes are attached to the brushing roll to prevent the generation of heat by the friction between the brushing roll and the brushed roll. However the density of the bristle is unevenly distributed, which causes a brushing pattern on the surface of the rolls of the mill, which is printed on the strip surface as unevenly distributed roughness.
Japanese Patent Publication laid open No. 57-75212 discloses a method wherein an abrasive grain is incorporated in the brush of the brushing roll to assist in removing foreign objects and to increase the rigidity of the bristle.
However these measures in turn can cause defects on the surface of the rolls of the mill.